The present invention relates to a connector mounted on a board.
A conventional connector 60 shown in FIGS. 8 and 9 has a housing 61 and a plurality of connecting terminals 62 extending from the housing 61. The connector 60 can be mounted by soldering on a wiring board 63 having a plurality of through holes 64, which is shown in FIGS. 8 and 9. Each of the connecting terminals 62 of the connector 60 having been mounted on the wiring board 63 is inserted in one of the through holes 64.
The connector 60 can be used as an automobile part. The connector 60 used as an automobile part has been required to be smaller in size in recent years. To meet this requirement, there is a tendency to decrease not only for the size of the connecting terminal 62 but also to decrease the pitch A1 between the adjacent connecting terminals 62. The connector 60 used as an automobile part has also been required to have very high environment resistance, i.e., thermal shock resistance. This is because automobile parts are exposed to harsh environments, such as blazing sun and extreme cold.
When the pitch A1 between the adjacent connecting terminals 62 is decreased, it is necessary to decrease the size of a land 65 provided on the wiring board 63. However, when the connector 60 is subjected to a thermal shock, a decrease in the size of the land 65 easily produces a crack in a solder portion 66 in which the connecting terminal 62 connects with the wiring board 63. That is to say, the reliability of the solder portion 66 decreases. A crack is liable to be produced especially when the wiring board 63 on which the connector 60 is mounted is what is called a one side board having the land 65 only on one side (see FIG. 10). The reason why the crack is produced is presumed to be that thermal stress is applied to the solder portion 66 by a difference between the coefficient of thermal expansion of the connecting terminal 62 and that of the wiring board 63.